Methods of Manufacturing Golf Club Heads

ABSTRACT

A golf club head comprising at least one part manufactured via a metal injection molding process, and attached to another part of the golf club head via electrical resistance welding or electrical resistance brazing, is disclosed herein. The present invention is also directed to a method of making said golf club head, the method comprising the steps of providing a first golf club head part made from a first metal material, metal injection molding a second golf club head part from a second, different metal material, and electrical resistance welding or electrical resistance brazing the second golf club head part to the first golf club head part to form a combined part.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation in part of U.S. patentapplication Ser. No. 16/353,347, filed on Mar. 14, 2019, which is acontinuation of, and claims priority to, U.S. patent application Ser.No. 15/950,789, filed on Apr. 11, 2018, and issued on Jul. 2, 2019, asU.S. Pat. No. 10,335,653, the disclosure of each of which is herebyincorporated by reference in its entirety herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method of manufacturing one or moreportions of a golf club head via metal injection molding and electricalresistance welding processes. In particular, the present inventionrelates to metal injection molded face cups and weights for golf clubheads, and bonding components of the golf club heads together usingelectrical resistance welding or brazing.

Description of the Related Art

Prior art iron-type golf club head parts, particularly faces, are madeby investment casting or machining sheet metal to specification. Theseprocesses are time consuming, have significant design constraints, andcan be cost-prohibitive for manufacturers. For example, investmentcasting a part for a golf club head requires the part to have minimumwall thicknesses, transitions, undercuts, and draft angles; theprocessing time for investment casting is also lengthy, limiting theproduction capacity of a manufacturer. Similarly, machining parts fromsheet metal requires significant time and produces unwanted waste, asexcess material must be removed from the part under manufacture.

If a manufacturer wishes to use different materials for different partsof the golf club head (e.g., a titanium alloy face with a stainlesssteel body), the waste produced, and the complexity of building the clubhead, increases. Prior art multi-material iron heads with multiple metalcomponents (e.g., face, body, and internal weighting) are joined usingtraditional welding processes such as tig welding, plasma welding, andlaser welding. Each of these welding processes produces a weld bead ofvarying size and consumes weld rods to join the components. Atraditional player's iron chassis, especially in the short irons, iscompact, with thin sole widths and thin topline thicknesses. Due to thesize constraints of the chassis, multi-material constructions arechallenging in a player's iron head shape because traditional weldingprocesses require slightly larger head shapes or post weld machining tojoin all of the components in a small compact shape.

There is therefore a need for relatively quick and efficient processesof manufacturing and bonding metal golf club parts to allow forintricate thickness patterns and secure bonding, reduce the overall timeof production, and minimize material waste.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a method of manufacturing a facecomponent for a golf club head, and particularly iron-type golf clubheads, using metal injection molding. This process overcomes existingconstraints and allows for multi-material designs, thin wall and hinges,and radical variable face thickness patterns.

Another aspect of the present invention is a method of manufacturing aface component for a golf club head by co-injection molding a titaniumalloy substructure to increase coefficient of restitution (COR) whilemaintaining the COR at the geometric face center.

Yet another aspect of the present invention is a method of electricalresistance welding one or more metal pieces together to form at least aportion of a golf club head.

Yet another aspect of the present invention is a method of electricalresistance brazing one or more metal pieces together to form at least aportion of a golf club head.

Another aspect of the present invention is a method comprising the stepsof casting from a first metal material a golf club face componentcomprising a striking face, a rear surface opposite the striking face,and a recess disposed in the rear surface, metal injection molding aweight plate from a second metal material, the weight plate havingapproximately the same size and shape as the recess, providing a brazealloy material, placing the braze alloy material in the recess, placingthe weight plate within the recess on top of the braze alloy material toform a combined part, and electrical resistance brazing the weight plateto the face component, wherein the step of casting the face componentcomprises integrally forming a plurality of scorelines in the strikingface, and wherein the second metal material has a higher density thanthe first metal material.

In some embodiments, the weight plate may have a thickness of less than0.075 inch, a mass of 10-25 grams, and a density of 18-18.5 g/cc. Inother embodiments, the braze alloy material may be a brazing paste or abraze preform foil. In any of the embodiments, the braze alloy materialmay comprise silver and copper, and in a further embodiment a majorityof the braze alloy material may be composed of silver and copper. Inother embodiments, the first metal material may be selected from thegroup consisting of steel and titanium alloy, and the second metalmaterial may comprise tungsten. In another embodiment, the method mayfurther comprise the step of applying at least one finish to thecombined part. In some embodiments, each of the first and second metalmaterials may be selected from the group consisting of steel andtitanium alloy. In another embodiment, the method may further comprisethe step of permanently affixing the combined part to a golf club headbody, which may an iron-type body.

Yet another aspect of the present invention is a method comprising thesteps of providing an electrical resistance system comprising a pair ofelectrodes, placing between the pair of electrodes a golf club headcomprising a first piece composed of a first metal material, a secondpiece composed of a second, braze alloy material, and a third piececomposed of a third material, wherein the first piece is at leastpartially disconnected from the second and third pieces, and wherein thesecond piece is disposed between the first and third pieces, applyingpower to a plurality of regions of the golf club head so that the brazealloy material melts between and connects the first and third pieces,and removing the golf club head from the electrical resistance system.

In one embodiment, the method may further comprise the step of metalinjection molding at least one of the first piece and the third piece,which step may occur before the step of placing the golf club headbetween the pair of electrodes. In a further embodiment, the step ofmetal injection molding at least one of the first piece and the thirdpiece may comprise co-injection molding two different metal alloys. Inother embodiments, the golf club head may be an iron-type head. In anyof the embodiments, the braze alloy material may be a brazing paste or abraze preform foil, and the braze alloy material may comprise, or besubstantially composed of, silver and copper. Also in any of theembodiments, the first metal material may be selected from the groupconsisting of steel and titanium alloy, and the third metal material maycomprise tungsten.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a flow chart describing a metal injection molding methodaccording to the present invention.

FIG. 2 is a side perspective view of an iron-type golf club head of thepresent invention.

FIG. 3 is a front elevational view of the face component shown in FIG.2.

FIG. 4 is a rear elevational view of the face component shown in FIG. 3.

FIGS. 5-8 are side perspective views of alternative embodiments of theface component manufactured according to MIM co-molding methods of thepresent invention.

FIG. 9 is a side perspective view of an exemplary sole weight componentmanufactured according to MIM co-molding methods of the presentinvention.

FIG. 10 is a cross-sectional view of the embodiment shown in FIG. 9along lines 10-10.

FIG. 11 is an exploded view of the embodiment shown in FIG. 9.

FIG. 12 is a rear perspective view of a high density weighting plateaccording to another embodiment of the present invention.

FIG. 13 is a side plan view of the embodiment shown in FIG. 12.

FIG. 14 is a rear plan view of an alternative face component accordingto the present invention.

FIG. 15 is a rear plan view of the weighting plate shown in FIG. 15engaged with the face component shown in FIG. 14.

FIG. 16 is an illustrated flow chart describing a preferred method ofelectrical resistance welding pieces of a golf club head togetheraccording to the present invention.

FIG. 17 is an enlarged view of the highlighted section of theillustrated method shown in FIG. 16.

FIGS. 18-19 are views of an alternative embodiment of the face componentshown in FIG. 14.

FIG. 20 is a side perspective view of a weighting plate.

FIGS. 21-22 are views of a braze alloy material.

FIG. 23 is a side perspective view of the weight piece shown in FIG. 20disposed on the face component shown in FIG. 18.

FIGS. 24-25 are views of the braze alloy material shown in FIGS. 22-22engaged with the embodiment shown in FIG. 23.

FIGS. 26-28 are views of the embodiment shown in FIGS. 24-25 engagedwith electric resistance equipment.

FIG. 29 is a flow chart describing a preferred method according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to use of the metal injection molding(MIM) process illustrated in FIG. 1 to manufacture one or more pieces ofa golf club head. First, a metal powder is mixed with a polymer, whichis used as a carrier and binding agent 110; this mixture is thensolidified to create a specialized compound 120. The specializedcompound is then processed through an injection-molding machine into aninjection mold to create the desired part, which is commonly referred toas a “green state” part 130. The green state part is placed in adebinding oven to melt out most of the polymer, leaving just enoughpolymer to hold the metal particles together 140; this product iscommonly referred to as a “brown state” part. In the final step, thebrown state part is sintered in a vacuum oven 150. The sintering processremoves the remaining polymer material from the part and fuses the metaltogether through a heat treatment process, resulting in a finished part.The part will typically shrink by approximately 20% during the sinteringstep 150.

When MIM is used to manufacture one or more golf club head parts (e.g.,face components, weights, reinforcement plates), the process increasesthe production rate of the part, thereby reducing the unit cost of thepart and the club head as a whole. The MIM process also allows forhigh-throughput manufacture of parts with more intricate thicknesspatterns and inner/outer mold line designs than existing golf club headparts, which improves the overall performance of the part. This isparticularly helpful when manufacturing face components 30 and otherportions of iron-type golf club heads 10, such as the exemplary irongolf club head disclosed in FIG. 2, as there is less space within aniron head in which to distribute the available mass, and processconstraints limit the extent to which complicated thickness patterns canbe refined in prior art manufacturing processes like casting or forging.

Some examples of face components manufactured via MIM are shown in FIGS.2-4. In this preferred embodiment, the face component 30 is a face cuphaving a striking face 32 with scorelines 40 and a rear surface 34opposite the striking face. The face component 30 also includes an upperextension portion 31, a side extension portion 33, and a sole extensionportion 35, all extending away from the striking face 32. The scorelines40 are preferably formed during the MIM process instead of being addedby a separate process (e.g., machining, laser cutting, spin-milling)after the part is completed. The face component 30 is permanentlyaffixed to a body 20 comprising a top line 22, a sole 24, a heel side 26with a hosel 25, a toe side 28 opposite the heel side 26, and an opening(not shown) sized to be covered by the face component.

MIM can also be used to co-injection mold dissimilar materials andcreate elaborate thickness and weighting patterns in the face components30 described above. In alternative embodiments, shown in FIGS. 5-8, asubstructure 50 is co-molded via MIM to the rear surface 34 of thestriking face 32. As shown in FIG. 5, the substructure 50 is a latticeextending across the entire rear surface 34 of the face component 30. InFIG. 6, the substructure 50 is a solid wall extending only across thelower third of the area of the rear surface 34, though it may in otherembodiments cover the lower half of the rear surface 34 below thegeometric center 45 of the striking face 32. In FIG. 7, the substructure50 is composed of four quadrants 52, 54, 56, 58 covering upper toe 36,upper heel 37, lower toe 38, and lower heel regions 39 of the rearsurface while leaving uncovered small areas around the geometric centerof the rear surface and the vertical and horizontal axes 46, 48extending through the geometric center 45. In FIG. 8, the substructure50 is a circular piece centered around the geometric center 45 of therear surface 34.

The substructure 50 preferably is composed of a titanium alloy, thoughin other embodiments it may be a higher density material such astungsten alloy, while the rest of the face component 30 is composed of asteel material. This substructure 50 allows the manufacturer tofine-tune the coefficient of restitution (COR) across the striking face32 while maintaining a high COR (preferably the USGA maximum) at thegeometric center 45 of the striking face 32, and helps to decouple theCOR values from the golf club head 10 center of gravity (CG). Thesubstructure 50 preferably increases the COR at low, central regions ofthe striking face 32, in addition to the heel and toe regions.

In addition to its use in manufacturing high-performance face components30, MIM co-molding can be used to combine dissimilar materials in other,more highly weighted areas of the iron-type golf club head 10 of thepresent invention. For example, FIGS. 9-11 disclose a 17-4 stainlesssteel cover 62 that is co-molded around a tungsten alloy weight 64,forming a sole weight 60 and rendering secondary bonding or weldingprocesses to assemble the weight unnecessary.

In yet another embodiment, shown in FIGS. 12-15, MIM is used to create athin, high-density weighting plate 70 that is disposed within a shallowrecess 42 in the upper toe region 36 of the rear surface 34 of thestriking face 32. The plate preferably 70 has a thickness of less than0.10 inch, and more preferably less than 0.075 inch, and a mass rangingfrom 10-25 grams, and is composed of a tungsten alloy material with adensity of 16-18.5 g/cc, and preferably a density of 18-18.5 g/cc.

In each of the embodiments disclosed herein, the pieces of the golf clubhead 10 that are made of dissimilar materials may be affixed to oneanother via the process of electrical resistance welding (ERW). ERW hasa fast lead time, consumes fewer materials than traditional welding, andresults in a negligible weld bead between the parts being attached toone another, thus using up less discretionary mass within the golf clubhead. The ERW process creates a reliable electro-mechanical bond betweenthe two components that is comparable to traditional welding in standarddurability testing.

For example, a first method for affixing the plate 70 and the facecomponent 30 disclosed in FIGS. 12-15 to one another using ERW isillustrated in FIG. 16. As shown in FIG. 15, the plate 70 may besemi-permanently fixed to the face component 30 at one or more locationswith tack welds 80, 82 to hold the plate 70 in place prior to applyingthe ERW process, but this step is optional. The ERW method 200 comprisesthe steps of cleaning the electrode(s) of the welder 210, placing thegolf club head pieces to be joined between the electrodes of the welder220, applying power for approximately 1 second to each region of thegolf club head to be joined 230, removing the golf club head andapplying a first finish 240, and applying a second finish 250 to coverthe small weld bead 90 created by the ERW method 200, an example ofwhich (prior to the finishing steps 240, 250) is shown in FIG. 17.

In another, preferred embodiment, a plate 70 made of a high-densitymaterial is affixed to the rear surface 34 of the striking face 32 usingan electrical resistance brazing (ERB) method 400. The ERB method 400,which has several similarities to the ERW method 200, requires a lowercurrent than the ERW method 200, thus reducing the likelihood of leavingunwanted marks on the face component 30. The ERB method 400 eliminatesthe need for the club head 10 to undergo secondary processes, such asmachining, painting, or other means of covering the marks, to remove theunwanted marks, and permits casting of scorelines 40, which is a morecost effective method of adding scorelines 40 to the face component 30than machining.

The preferred method 400 of the present invention is shown in FIG. 29,with component parts of the golf club head 10 illustrated in FIGS.18-28. In a first step 410, a face component 30 with a first density isprovided, and in a second step 420, a plate 70 with a second densitythat is higher than the first density is provided. In a third step 430,a braze alloy material 85 is placed between, and in direct contact with,the face component 30 and the plate 70 to create a combined part 95. Thebraze alloy 85 preferably is in the form of a brazing paste or a brazepreform foil, and comprises mostly silver and copper. In this third step430, the braze alloy material 85 and the plate 70 preferably are placedinto a shallow recess 42 in the rear surface 34 of the face component30. In a fourth step 440, electrodes 310, 315 of an electrical brazingsystem 300 are pressed to either side of the combined part 95, with oneelectrode 315 contacting the lower density face component 30, and theother electrode 310 contacting the higher density plate 70. In a fifthstep 450, a current is passed through the electrodes 310, 315, meltingthe braze alloy 85 to join the face component 30 to the plate 70. Thismethod 400 allows for the attachment of a high-density material to theface component 30 of a golf club using lower currents.

Though the embodiments disclosed herein focus on iron-type golf clubhead manufacture, the methods and designs disclosed herein may beapplied to any type of golf club head, including drivers, fairway woods,hybrids, wedges, utility irons, and putters.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claims. The section titles included herein also arenot intended to be limiting. Therefore, the embodiments of the inventionin which an exclusive property or privilege is claimed are defined inthe following appended claims.

We claim:
 1. A method comprising the steps of: casting from a firstmetal material a golf club face component comprising a striking face, arear surface opposite the striking face, and a recess disposed in therear surface; metal injection molding a weight plate from a second metalmaterial, the weight plate having approximately the same size and shapeas the recess; providing a braze alloy material; placing the braze alloymaterial in the recess; placing the weight plate within the recess ontop of the braze alloy material to form a combined part; and electricalresistance brazing the weight plate to the face component, wherein thestep of casting the face component comprises integrally forming aplurality of scorelines in the striking face, and wherein the secondmetal material has a higher density than the first metal material. 2.The method of claim 1, wherein the weight plate has a thickness of lessthan 0.075 inch, a mass of 10-25 grams, and a density of 18-18.5 g/cc.3. The method of claim 1, wherein the braze alloy material is a brazingpaste or a braze preform foil.
 4. The method of claim 1, wherein thebraze alloy material comprises silver and copper.
 5. The method of claim4, wherein a majority of the braze alloy material is composed of silverand copper.
 6. The method of claim 1, wherein the first metal materialis selected from the group consisting of steel and titanium alloy. 7.The method of claim 1, wherein the second metal material comprisestungsten.
 8. The method of claim 1, further comprising the step ofapplying at least one finish to the combined part.
 9. The method ofclaim 1, wherein each of the first and second metal materials isselected from the group consisting of steel and titanium alloy.
 10. Themethod of claim 1, further comprising the step of permanently affixingthe combined part to a golf club head body.
 11. The method of claim 10,wherein the golf club head body is an iron-type body.
 12. A methodcomprising the steps of: providing an electrical resistance systemcomprising a pair of electrodes; placing between the pair of electrodesa golf club head comprising a first piece composed of a first metalmaterial, a second piece composed of a second, braze alloy material, anda third piece composed of a third material, wherein the first piece isat least partially disconnected from the second and third pieces, andwherein the second piece is disposed between the first and third pieces;applying power to a plurality of regions of the golf club head so thatthe braze alloy material melts between and connects the first and thirdpieces; and removing the golf club head from the electrical resistancesystem.
 13. The method of claim 12, further comprising the step of metalinjection molding at least one of the first piece and the third piece,wherein the step of metal injection molding at least one of the firstpiece and the third piece occurs before the step of placing the golfclub head between the pair of electrodes.
 14. The method of claim 13,wherein the step of metal injection molding at least one of the firstpiece and the third piece comprises co-injection molding two differentmetal alloys.
 15. The method of claim 12, wherein the golf club head isan iron-type head.
 16. The method of claim 12, wherein the braze alloymaterial is a brazing paste or a braze preform foil.
 17. The method ofclaim 12, wherein the braze alloy material comprises silver and copper.18. The method of claim 17, wherein a majority of the braze alloymaterial is composed of silver and copper.
 19. The method of claim 12,wherein the first metal material is selected from the group consistingof steel and titanium alloy.
 20. The method of claim 12, wherein thethird metal material comprises tungsten.